Related Field
The present invention relates to a touch sensing system and, more specifically, to a touch sensing system for enabling touch input through an active stylus pen and a driving method thereof.
Discussion of the Related Art
A user interface (UI) is a device through which a person (user) can easily control electronic apparatuses. Typical examples of such user interface include a keypad, a keyboard, a mouse, an on-screen display (OSD), a remote controller having an infrared communication or radio frequency (RF) communication function and the like. User interface technology has developed to improve user sensitivity and operation convenience. Recently, user interfaces have evolved into a touch UI, a speech recognition UI, a 3D UI, etc.
The touch UI is essentially employed by portable information devices. The touch UI is implemented in such a manner that a touchscreen is configured on a screen of a display device. Such a touchscreen may be implemented as a capacitive type touchscreen. A touchscreen having a capacitive touch sensor senses touch input by sensing a capacitance variation according to input of a touchscreen driving signal, that is, a charge variation of the touch sensor when a user's finger or a conductive material touches (or approaches) the touch sensor.
The capacitive touch sensor may be implemented as a self-capacitance sensor or a mutual capacitance sensor. Electrodes of the self-capacitance sensor can be connected to respective sensor lines formed in one direction. The mutual capacitance sensor can be formed at intersections of sensor lines perpendicular to each other and having a dielectric layer interposed therebetween.
Recently, a stylus pen as well as a finger has been widely used to input commands in smartphones, e-readers and the like. The stylus pen has the advantage of more delicate input than a finger. The stylus pen may be classified into passive and active stylus pens. As to the passive stylus pen, less capacitance variation occurs at a contact point of the passive stylus pen and a touchscreen than an active stylus pen, and thus it may be difficult to detect a touch point. The active stylus pen self-generates a pen driving signal and outputs the generated pen driving signal to a contact point of the stylus pen and a touchscreen, and thus a touch point can be easily detected compared to the passive stylus pen.
When a stylus pen touches a touchscreen, a touch sensing system may execute various functions such as input signal processing in addition to touch input sensing. However, a conventional active stylus pen implements an additional communication block for transmitting writing pressure information to a touch module, as disclosed in Korean Patent No. 10-2014-0043299, thereby increasing manufacturing costs.